Hi guys, this is a general question about alternators.. I posted this on the Miata.net forums with no answers so I thought I would run this one past the true experts! My daily driver/beater "car" is a 1990 Mazda Miata with 223,000+ miles. Anyway when I start it up cold in the morning and throw the head lights on they are rather dim, if I hit the gas and bring the rpms up a little the alternator kicks in and starts generating electricity and they get bright again. I am just concerned that the alternator is failing, I checked the belts and the battery is a Mazda that I threw in there last year so its fine. I’m going to take the beater to Rehoboth Beach DE for Thanksgiving and don’t want any problems, gotta love 38 MPG!! My schedule recently changed and I have to be out and driving in the dark now so I’m not sure how long this has been happening! I appreciate any help with this one! Matt

 

Most alternators don't really provide a whole lot of power at idle, it is when they hit a higher RPM that they start to kick out the amps.

Do you have any aftermarket audio equipment or lighting?

Also, what kind of climate do you live in?

Could just be that your battery is not holding much of a charge, which could be a strain to your electrical system and a warning sign that you are really working the alternator.

Are you hearing any kind of whining noise or anything like that? A lot of places will do a free battery diagnostic if you bought it there (at least I know sears does, maybe some other places) and that way you could at least find out if that is the cause of all this.

 

I didnt even think to have AutoZone test it.. I dont hear any noise out of the alernator but some thing is going on with it! I live in WV, this morning it was in the low 60s so I dont think temp is an issue its almost like the bushings in there are going bad. I may just go ahead and install alternator just to be safe, I dont want it to fail on my late season vacation!

 

I had that problem with my 4runner and it was a cell going dead in the battery.

 

Changing out the Alt. is a pretty big expense if it is not needed. I would definitely have them check out the battery, especially because most of them come with a warrenty that should still cover it.

If there is a problem with the battery you may want to upgrate to something like an optima red top (since you don't really need the yellow top deep cycle unless you have a lot of audio or lighting mods - but the red tops can take a beating)

 

And FYI, Mazda batteries are notorously(sp?) bad from the get-go. I've gone round and round w/2, not 1 but 2 Mazda stealerships when I owned a '92 626 and a '941/2 RX7.1 battery was totally dead nuthing on my multimeter, and the other read under 9 volts....both were new.....go with a redtop atleast, you won't be dissapointed. My .02cents

 

scrap it and get one of those new ones that have the welder built in, really impress the Miata groups